PROJECT SUMMARY The rising rates of Human Papilloma Virus (HPV)-positive oropharyngeal cancers in the U.S. is a significant public health issue, while Hispanics show increased burden of this malignancy. Recent research suggests differences in oral microbiota between oropharyngeal cancer cases and controls, and between HPV+ and HPV- individuals. Nonetheless, research evaluating the role of oral microbiota on oral HPV infection, a main risk factor for oropharyngeal cancer, is scarce, and essential to develop effective prevention strategies. The proposed cross-sectional study will recruit 300 participants from sexually transmitted infections (STI) clinics of Puerto Rico. The specific aims of this application are to (1) characterize the oral microbiota profiles of patients with and without oral HPV infection, and (2) assess the association between species-level oral microbiota and oral HPV infection. Participants will provide saliva samples for oral HPV detection, following the NHANES methodology, and for oral microbiota analysis. Socio-demographic, behavioral, dental, and medical characteristics will be collected through an interviewer-administered questionnaire. Risk factors for oral HPV infection will be collected using the audio computer-assisted self-interview (ACASI) methodology, a useful tool for collecting sensitive risk behavior data. HPV typing will be performed by dot-blot hybridization using 38 type-specific probes, including oncogenic and non-oncogenic types, while for microbiota, genomic DNA extractions and 16S rDNA V4 amplifications will be done. Samples will then be subjected to Illumina Miseq sequencing and data analyses. To our knowledge, this is the first study that will assess the association between the oral microbiota and oral HPV infection among a homogenous Hispanic population. Accumulating evidence supports a biological plausibility for the association between the microbiota and HPV infection in various anatomical sites and with oral cancer; however, data on its relationship with oral HPV infection is limited. The identification of the oral microbiota?s role on oral HPV infection may provide essential information for the development of preventive public health strategies, as if research shows that the oral microbiota modulates oral HPV infection and oral carcinogenesis, the implications for oral cancer prevention and control strategies might be important.